Syringes for injecting various fluids into the arterial, venous, muscular and cavity structures of a patient via subcutaneous, percutaneous, intravascular and other types of injections are widely known and used. As herein use, the term "patient" generally refers to any individual subject to medical treatment, study or examination, including humans and so-called lower animals. Generally stated, a molded tubular body or barrel defines these syringes having a plunger at one end and a needle or other device for subcutaneous, percutaneous or other intravascular injection-type access at an opposite end. Retraction of the plunger fills the fluid chamber within the syringe with a desired fluid of the plunger, creating a vacuum and drawing fluid therein. Once filled to the desired volume of fluid, the plunger can be advanced within the barrel to force the fluid through the needle or other device subcutaneously, percutaneously or otherwise disposed appropriately to introduce the fluid within the patient.
Such syringes have been enormously useful in promoting and maintaining the health of humankind and in treating a variety of ailments, especially as hand-held and manually manipulated syringes. Such devices have also been adapted for diagnostic purposes, such as, for example, in angiographic applications. There, contrast media is injected into a patient for diagnosis of any number of different conditions. Such latter applications are more commonly performed today using machine-driven and/or automated devices controllably to inject the contrast media. Also, in such latter applications, reusing the syringe for multiple injections of contrast media into the same patient is desirable for many reasons, for example, to reduce costs, avoid entrained air that can lead to embolisms and minimize the examination time to avoid pericatheter thrombus.
However, these devices have the disadvantage that after they advance the plunger while the needle or other device remains subcutaneously, percutaneously or otherwise disposed, any retraction of the plunger draws bodily fluids back into the syringe. While this has always been a problem, the consequence of the HIV virus and acquired autoimmunity deficiency syndrome (AIDS) has made such backfilling fraught with dire results if the contaminants withdrawn are not otherwise contained.
Also, particularly in machine-driven and/or automated devices, dust, oils and latent biological matter from previous use are usually present near the interface between the drive mechanism and the syringe and surrounding structures, such as pressure jackets that hold the syringe. Thus, an additional disadvantage of the syringes of the prior art was that such contaminants can enter the syringe body and adhere to the inner walls of the syringe, with the possible introduction of such contaminants into the fluid chamber and, ultimately, the patient. This could result in cross-contamination of certain diseases from patient to patient such as Hepatitis B, Hepatitis C, AIDS and other blood-borne pathogens.
Because of these drawbacks, especially bodily fluids from previous patients becoming entrained into the syringe upon withdrawal of the plunger in diagnostic uses, it is typically not recommended that the syringe be used for more than one injection of contrast material. Although this reduces contamination of the mechanisms used to drive the plunger and contaminants entering the syringe from the drive mechanism or other sources from the open end of the syringe, the safety of the patient is compromised. Each time a new syringe is used, an opportunity exists for air to enter the fluid in communication with the patient, thus leading to the potential for an embolism. Also, in especially angiographic or vascular studies, prolonging the examination can result in pericatheter thrombus.
An approach to partially addressing these drawbacks, at least regarding automated or mechanical applications, is shown in U.S. Pat. No. 4,677,980. This reference shows an angiographic injector system having two angiographic injectors situated on a turret. Each injector is provided with a releasable connector for connecting the plunger to a driving mechanism for an injection operation and disconnecting the plunger from the driving mechanism after the injection operation so as not to draw body fluids of a patient back into the syringe.
While effective when used properly, the device taught by U.S. Pat. No. 4,677,980 does not guarantee the containment of pathogens borne in bodily fluids within the syringe. Much discretion remains with the operator of the injector mechanism and is still possible that withdrawal of the plunger can occur while the injector syringe remains in fluid communication with the venous, arterial or muscular system or cavity structures of the patient, thereby allowing bodily fluids to enter the syringe. Although the syringe is usually discarded after a single use on a single patient, the risk remains that the withdrawn bodily fluids may pass past the sides of the plunger to the exposed, non-sterile base of the plunger connected to the driving mechanism. The resulting contamination of the driving mechanism creates significant problems in cleaning, such as wasted time and lost machine productivity. Also, there is no effective method of ensuring that contaminants do not enter the syringe from the drive mechanism or otherwise.
Perhaps more important, the use of a new syringe for each contrast media injection requires repeated operations of disconnecting fluid communication with the patient from the old syringe, adding fluid to the new syringe and reestablishing fluid communication with the new syringe to the patient, each operation introducing the risk of embolisms and pericatheter thrombus.
Other approaches to avoid contamination exist, although none solve the aforementioned problems. One example is U.S. Pat. No. 4,511,534, which shows a liquid transfer device comprising a one-piece molded pipette plate having some pipette-type barrels extending downwardly. An annular upstanding boss surrounds the upper end of each barrel and support flange extending about the perimeter of the pipette plate. An elastic membrane extends over and rests on each annular boss. A membrane retaining plate, having through passages disposed in alignment with a barrel or pipette on the pipette plate and having a downwardly protruding boss, surrounds each aperture and extends in the respective upstanding boss on the pipette plate. Connecting means maintains the retaining plate in a first position compared with the pipette plate, where the bosses engage the elastic membrane with minimal tension, and a second position, where the bosses on the retaining plate and the pipette plate clamp the elastic membrane under tension with part of the elastic membrane extending into each of the pipettes' barrels.
However, in U.S. Pat. No. 4,511,534, the membrane is not shown as applicable to a syringe application. More important, its membrane is in direct contact with the fluid, providing no intermediate volume isolating the fluid chamber from the open end of the assembly. With such an arrangement, surface treatments, such as powder often present on elastomeric membranes, would be in contact with the fluid to be injected into the patient. Also, extraneous outside contaminants are not fully isolated.
The known prior art is thus lacking a syringe with means designed to isolate a sterile inner chamber of a syringe from contamination that might otherwise enter the syringe from various sources, such as from the drive mechanism into the open rear end of the syringe. The barrier means or membrane of the present disclosure prevents such further contamination. Also, since the barrier means of the present disclosure does not come into direct contact with the contrast medium or the like, reactions of patients that may be sensitive to the barrier means, for example, a latex membrane, is eliminated.
Also, an important advantage of the present disclosure is that the syringe herein revealed can be used multiple times on a single patient. Since the possibility of cross-contamination and air emboli injection is most acute during the setup procedures used with the installation of new syringes, these dangers are largely eliminated.